I'm in the market for a quad of SED 'winged C' KT88s and have been looking around on line. Most of the tubes I've found are being shipped in plain white boxes with the '=C=' logo stamped on the bottom of the box. I seem to remember that that SED EL34s that were being shipped in white boxes were inferior to the ones that were being shipped in the factory (red, black & white) box. There was something about the white box tubes being 'b grade' tubes that were sold in bulk and then repackaged by various sellers. Anyway, does anyone know anything about the quality of the white box SED KT88s? Are they 'A grade' tubes, or in some way inferior? Thanks,

IMO, you should pass SED (=C=) KT88s up, regardless of packaging. The tube is not particularly good. :( OTOH, the SED 6550C is a good tube. The current production KT88 varieties to look into are the "reissue" GEC and the ElectroHarmonix, both of which are made in New Sensor's Saratov, Russia, plant.

I'm not as expert on newer KT88's as Eli, but have heard many good things from trustworthy sources about the EH KT88, as well.

One thing, though, is I've never heard a 6550 as near to my liking as a good KT88 for hifi purposes (perhaps in guitar and bass amplifiers it would be different). KT88's provide noticeably better articulation in the low mids and down to my ear--ymmv.